This invention relates generally to switching systems, and more particularly, to cross point switching arrays utilized remanent reed switches.
Several remanent reed switch cross point switching matrices are known; however, common to the known switching matrices is the problem of magnetic interaction between adjacent switches in the matrix. In an attempt to reduce the magnetic interaction between adjacent switches, magnetic shields between adjacent switches and high permeability magnetic paths around individual switches have been utilized to minimize flux leakage. The high permeability path is generally provided by passing the remanent reed switches through a shunt plate so that the magnetic flux is concentrated by the shunt plate at the contact gap in the reed switch. The magnetic path between the ends of the reed switch and the shunt plate is completed by a magnetic structure, such as yoke, magnetically coupling the shunt plate to the ends of the reed switches, or through the use of ferromagnetic leads that serve both to interconnect the reed switches electrically and provide a magnetic path between the reed switches. Typical prior art cross point switching devices are illustrated in U.S. Pat. Nos. 3,789,332 and 3,439,301.
While the prior art switching devices provide a way to achieve cross point switching with very little magnetic interaction between switches, the use of magnetic shields and yokes results in a relatively large,, complex and costly structure, while ferromagnetic leads are difficult to solder thereby resulting in a structure that is difficult to manufacture and repair.
Accordingly, it is an object of the present invention to provide a reed switch cross point matrix assembly that overcomes many of disadvantages of the prior art matrix assemblies.
It is another object of the present invention to provide a cross point matrix assembly that eliminates the need for ferromagnetic yoke, ferromagnetic leads or magnetic shields to minimize interaction between adjacent switches.
It is yet another object of the present invention to provide a compact cross point switching matrix that is relatively simple and inexpensive to fabricate.
In accordance with a preferred embodiment of the invention, a plurality of coil forms are mounted on a magnetic shunt plate. Electromagnetic coils are wound around the coil forms, with the windings of adjacent coil forms being wound in opposite direction. A plurality of remanent reed switches are arranged in a straight line disposed at a 45.degree. angle with respect to the coordinates of the matrix.
The ends of the reed switches pass through a pair of "potato grater" end plates fabricated from a magnetically permeable material and disposed on opposite sides of the shunt plate to provide a high permeability magnetic path between the ends of the reed switches. The end plates serve as magnetic coupling plates between switches to minimize flux leakage, thereby permitting the reed switches to be placed close together without causing interaction.
Electrical connection to the reed switches is made on one side of the assembly by a plurality of parallel conductors interconnecting the reed switches in each row. Connection to the other side of the switches is made by a second plurality of parallel conductors running in a direction perpendicular to the first conductors and interconnecting the switches in each column. The interconnecting conductors may be conductive straps, wires or printed circuit conductors.